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Building on Olander's work on algebraic spaces, we prove Orlov's representability theorem relating fully faithful functors and Fourier--Mukai transforms between the bounded derived category of coherent sheaves to the case of smooth, proper,…

Algebraic Geometry · Mathematics 2024-05-31 Fei Peng

This work studies $t$-structures for the derived category of quasi-coherent sheaves on a quasi-compact quasi-separated algebraic stack. Specifically, using Thomason filtrations, we classify those $t$-structures which are generated by…

Algebraic Geometry · Mathematics 2025-07-04 Pat Lank

We look at spaces of infinite-by-infinite matrices, and consider closed subsets that are stable under simultaneous row and column operations. We prove that up to symmetry, any of these closed subsets is defined by finitely many equations.

Algebraic Geometry · Mathematics 2016-02-26 Rob Eggermont

With the long-term goal of proving local structure theorems of algebraic stacks in positive characteristic near points with reductive (but possibly non-linearly reductive) stabilizer, we conjecture that quotient stacks of the form…

Algebraic Geometry · Mathematics 2023-09-06 Jarod Alper , Jack Hall , David Benjamin Lim

We generalize the notion of a small sheaf of sets over a topological space or manifold to define the notion of a small stack of groupoids over an \'etale topological or differentiable stack. We then provide a construction analogous to the…

Algebraic Topology · Mathematics 2012-03-28 David Carchedi

We give necessary and sufficient conditions for a cdh sheaf to satisfy Milnor excision, following ideas of Bhatt and Mathew. Along the way, we show that the cdh infinity-topos of a quasi-compact quasi-separated scheme of finite valuative…

Algebraic Geometry · Mathematics 2020-10-02 Elden Elmanto , Marc Hoyois , Ryomei Iwasa , Shane Kelly

Consider a measured equivalence relation acting on a bundle of hyperbolic metric spaces by isometries. We prove that every aperiodic hyperfinite subequivalence relation is contained in a {\em unique} maximal hyperfinite subequivalence…

Dynamical Systems · Mathematics 2016-12-13 Lewis Bowen

Motivated by the analysis and geometry of metric-measure structures in infinite dimensions, we study the category of extended metric-topological spaces, along with many of its distinguished subcategories (such as the one of compact spaces).…

Category Theory · Mathematics 2026-01-13 Enrico Pasqualetto , Timo Schultz , Janne Taipalus

A topological space is nonseparably connected if it is connected but all of its connected separable subspaces are singletons. We show that each connected first countable space is the image of a nonseparably connected complete metric space…

Metric Geometry · Mathematics 2009-11-05 T. Banakh , M. Vovk , M. R. Wójcik

We give a conceptual proof of the fact that if M is a complete submanifold of a space form, then the maximal integral manifolds of the nullity distribution of its second fundamental form through points of minimal index of nullity are…

Differential Geometry · Mathematics 2011-04-08 Carlos Olmos , Francisco Vittone

This paper proves a result on the existence of finite flat scheme covers of Deligne-Mumford stacks. This result is used to prove that a large class of smooth Deligne-Mumford stacks with affine moduli space are quotient stacks, and in the…

Algebraic Geometry · Mathematics 2016-09-07 Andrew Kresch , Angelo Vistoli

It is well-known that a metric space $(X, d)$ is complete iff the set $X$ is closed in every metric superspace of $(X, d)$. For a given pseudometric space $(Y, \rho)$, we describe the maximal class $\mathbf{CEC}(Y, \rho)$ of superspaces of…

General Topology · Mathematics 2022-06-06 Viktoriia Bilet , Oleksiy Dovgoshey

Notions and techniques of enriched category theory can be used to study topological structures, like metric spaces, topological spaces and approach spaces, in the context of topological theories. Recently in [D. Hofmann, Injective spaces…

Category Theory · Mathematics 2008-07-28 Maria Manuel Clementino , Dirk Hofmann

We discuss the space of complex exponential maps $\Ek\colon z\mapsto e^{z}+\kappa$. We prove that every hyperbolic component $W$ has connected boundary, and there is a conformal isomorphism $\Phi_W\colon W\to\half^-$ which extends to a…

Dynamical Systems · Mathematics 2007-05-23 Dierk Schleicher

We classify thick subcategories of the $\infty$-categories of perfect modules over ring spectra which arise as functions on even periodic derived stacks satisfying affineness and regularity conditions. For example, we show that the thick…

Algebraic Topology · Mathematics 2015-08-12 Akhil Mathew

This paper investigates sufficient and necessary conditions for the existence of a homotopy equivalence between two finite simplicial complexes from an algorithmic point of view. As a result, the conditions are formulated in terms of the…

Algebraic Topology · Mathematics 2025-12-25 Mária Šimková

This is the first in a series of papers devoted to foundations of topological stacks. We begin developing a homotopy theory for topological stacks along the lines of classical homotopy theory of topological spaces. In this paper we go as…

Algebraic Geometry · Mathematics 2007-05-23 Behrang Noohi

We present new completeness conditions for exponential systems on the complex plane in Banach algebras of continuous functions on a compact with a connected complement that are simultaneously holomorphic in the interior of this compact if…

Complex Variables · Mathematics 2023-06-29 B. N. Khabibullin , E. G. Kudasheva

Uniformly star superparacompactness, which is a topological property between compactness and completeness, can be characterized using finite-component covers and a measure of strong local compactness. Using these finite-component covers and…

General Topology · Mathematics 2025-05-02 Argha Ghosh

A ringed finite space is a ringed space whose underlying topological space is finite. The category of ringed finite spaces contains, fully faithfully, the category of finite topological spaces and the category of affine schemes. Any ringed…

Algebraic Geometry · Mathematics 2015-11-20 Fernando Sancho de Salas